This invention relates to optical transmission systems in general and specifically to fibre optic networks employing wavelength division multiplexing.
Telecommunications network service providers have attempted to keep pace with the exponential increase in demand for telecommunications bandwidth by relying on optical fibre digital networks.
Since 1990, the North American long distance infrastructure has been based on an optical fibre backbone known as SONET (Synchronous Optical NETwork). SONET payloads are time division multiplexed (TDM) digital signals. In North America, OC-48 optical fibres have been used, capable of supporting a SONET signal format of up to STS-48, operating at a maximum bit rate of 2.4 Gbit/s. Each OC-48 fibre is able to support approximately 32,000 simultaneous telephone calls, or 48 channels operating at the maximum electrical transmission digital signal DS-3. The current technology now supports the use of OC-192 fibres having four times the capacity of OC-48 fibres.
More recently, a technique known as wavelength division multiplexing (WDM) has been proposed to significantly increase bandwidth along the optical fibre backbone already installed. WDM involves the introduction of more than one carrier signal within a single optical fibre. These carrier signals are identified by a defining wavelength in the range of 1540 nm to 1610 nm during which the OC-48 fibre has a minimal loss characteristic. The signals are presently separated from neighbouring signals on either side by plus or minus 0.15 nm. In long-haul networks, the signals are divided into two bands, typically denoted Blue (1540 nm to 1555 nm) and Red (1555 nm to 1570 nm) respectively to provide bi-directional transmission capability. In metropolitan WDM networks, duplicate sets of fibres may be used to provide bi-directional transmission capability. Each carrier signal may be modulated by digital data at up to STS-48 data rates. In the case of dense WDM (DWDM) systems, there may be as many as 32 separate channels per fibre, although this number will increase as the technology continues to improve.
While solving the problem of bandwidth availability, at least for the present, WDM presents a significant challenge to the network service provider in terms of determining the physical connectivity of the network for the purposes of maintenance, fault isolation, network-fill usage, performance monitoring and protection readiness.
First, the WDM network necessarily entails an increase in the complexity of the network topology which is proportionate to the increase in traffic capacity of such networks over non-WDM optical networks and even electrical communications networks.
Second, network topology has conventionally been charted by manual datafilling techniques, that is, additions to, deletions from or other modifications to the existing network topology were recorded manually at the network""s central office. Even with non-WDM networks, such techniques were frequently characterized by inaccuracy due to errors in the manual keying of the connectivity data and obsolescence since the manually entered data can become easily out of date as the physical fibre connections are constantly changed. Not infrequently, a correct and up to date topology was not recorded until all or part of the network failed and the topology was manually retraced during the repair effort. Moreover, manual datafilling is an expensive and time-consuming endeavour.
Third, because optical networks are inherently transparent to the embedded payload signal, any payload could in theory be carried along the network without extensive hardware redeployment when the service is changed. This same transparency characteristic means that the network service provider is unable to accurately monitor the signal connectivity of the network, even with an accurate topology of the various network elements or nodes.
The challenges are even more significant in identifying and isolating faults along the network. Fault isolation and repair necessarily requires a detailed and accurate record of the network topology, which, as indicated above, is not often available when manual datafilling methods are used to maintain network connectivity data. More significantly, the increased traffic capacity and the transparency of WDM optical networks with regard to signal connectivity render obsolete such traditional fault isolation techniques as manual signal tracing and require the development of new techniques to identify and isolate network faults.
It is therefore desirable to provide a WDM network with the capability of determining the network""s physical topology and signal connectivity in an automated and ongoing manner.
It is also desirable to provide a WDM network with the capability of fault isolation in an automatic and ongoing manner.
It is further desirable to provide a WDM network where individual nodes can detect the connectivity of incoming optical signals and based on their own internal connectivity, broadcast downstream the new signal connectivity.
The invention may be summarized according to a broad aspect as a wavelength division multiplexed (WDM) network having a plurality of network nodes interconnected by WDM compatible optical fibre segments which carry a plurality of WDM compatible wavelengths capable of being modulated by signals, comprising: a configuration propagation system for propagating configuration data of each network node along the network; and a mapping processor for monitoring and processing the configuration data of each network node whereby the configuration for the entire network may be determined.
The invention may be summarized according to a second broad aspect as for use in a WDM network having a plurality of network nodes interconnected by WDM compatible optical fibre segments which carry a plurality of WDM compatible wavelengths capable of being modulated by signals, a configuration signal processor associated with at least one of the network node for generating configuration data, and mapping processor for determining the configuration of the entire network, a configuration signal containing the configuration data for modulating a WDM compatible configuration wavelength reserved throughout the network, whereby the configuration signal processor of a network node may insert configuration data into the configuration signal and the mapping processor may retrieve the configuration data from the configuration signal and determine the configuration of the entire network.
The invention may be summarized according to a third broad aspect as for use in a WDM network having a plurality of network nodes interconnected by WDM compatible optical fibre segments which carry a plurality of WDM compatible wavelengths a capable of being modulated by signals, a configuration signal containing configuration data for modulating a WDM compatible configuration wavelength reserved throughout the network, and a mapping processor for determining the configuration of the entire network,a configuration signal processor associated with a network node for generating configuration data and inserting the configuration data into the configuration signal, whereby the mapping processor may retrieve the configuration data for each network node from the configuration signal and determine the configuration of the entire network.
The invention may be summarized according to a fourth broad aspect as for use in a WDM network having a plurality of network nodes interconnected by WDM compatible optical fibre segments which carry a plurality of WDM compatible wavelengths capable of being modulated by signals, a configuration signal processor associated with at least one of the network nodes for generating configuration data and a configuration signal containing configuration data for modulating a WDM compatible configuration wavelength reserved throughout the network,a mapping processor for retrieving and processing the configuration data for each network node from the configuration signal,whereby the configuration for the entire network may be determined.
The invention may be summarized according to a fifth broad aspect as, for use in a WDM network having a plurality of network nodes interconnected by WDM compatible optical fibre segments which carry a plurality of WDM compatible wavelengths capable of being modulated by signals, a fault processor associated with at least one of the network nodes for generating fault data, and a fault isolation processor for monitoring and processing the fault data of each network node,a fault signal containing the fault data for modulating a WDM compatible fault wavelength reserved throughout the network, whereby the fault processor of a network node may insert fault data into the fault signal and the fault isolation processor may retrieve the fault data from the fault signal and identify and isolate faults in the entire network.
The invention may be summarized according to a sixth broad aspect as for use in a WDM network having a plurality of network nodes interconnected by WDM compatible optical fibre segments which carry a plurality of WDM compatible wavelengths capable of being modulated by signals, a fault signal containing fault data for modulating a WDM compatible fault wavelength reserved throughout the network, and a fault isolation processor for monitoring and processing the fault data of each network node,a fault processor associated with a network node for generating fault data and inserting the fault data into the fault signal, whereby the fault isolation processor may retrieve the fault data for each network node from the fault signal and isolate faults in the entire network.
The invention may be summarized according to a seventh broad aspect as for use in a WDM network having a plurality of network nodes interconnected by WDM compatible optical fibre segments which carry a plurality of WDM compatible wavelengths capable of being modulated by signals, a fault processor associated with at least one of the network nodes for generating fault data and a fault signal containing fault data for modulating a WDM compatible fault wavelength reserved throughout the network,a fault isolation processor for retrieving and processing the fault data for each network node from the fault signal, whereby faults in the entire network may be isolated.
The invention may be summarized according to an eighth broad aspect of a method of determining the configuration of a WDM network having a plurality of network nodes interconnected by WDM compatible optical fibre segments which carry a plurality of WDM compatible wavelengths capable of being modulated by signals and a mapping processor, comprising the steps of: at least one of the nodes determining its configuration; each of the at least one nodes reporting its configuration data to the mapping processor; and the mapping processor determining the overall configuration of the network from the configuration data received from the at least one nodes.
The invention may be summarized according to a ninth broad aspect as a method of determining the configuration of a WDM network having a plurality of network nodes interconnected by WDM compatible optical fibre segments which carry a plurality of WDM compatible wavelengths capable of being modulated by signals, comprising the steps of: reserving one of the WDM compatible wavelengths along the network; a first network node modulating the reserved wavelength on a fibre segment with which it is connected to a second network node with an out-of-band signal describing the in-band signals borne on the other wavelengths along the fibre segment; the first network node transmitting the out-of-band signal together with the in-band signals along the fibre segment from the first node to the second node; and the second network node reviewing the out-of-band signal received along the fibre segment and determining what in-band signals were transmitted along the fibre segment.
The invention may be summarized according to a tenth broad aspect as a method of determining the configuration of a WDM network having a plurality of network nodes interconnected by WDM compatible optical fibre segments which carry a plurality of WDM compatible wavelengths capable of being modulated by in-band signals, a configuration signal containing configuration data for modulating a WDM compatible configuration wavelength reserved throughout the network, configuration signal processors associated with each network node for generating configuration data specific to its associated network node, and a mapping processor for determining the configuration of the entire network, comprising the steps of: the mapping processor inserting a node-to-node message in the configuration signal; the configuration wavelength propagating the node-to-node message in the configuration signal to each network node immediately downstream of the network node; upon receipt of the node-to-node message in the configuration signal at a network node, the configuration signal processor associated with the network node: retrieving the configuration data reported by the immediately upstream configuration signal processor from the node-to-node message in the configuration signal; calculating the effect of its associated network node on the configuration data reported by the immediately upstream configuration signal processor; formatting the configuration data of its associated network node into a node-to-node message; and inserting the node-to-node message into the configuration signal; the mapping processor inserting a request message into the configuration signal; the configuration wavelength propagating the request message in the configuration signal to each network node in the network in turn; upon receipt of the request message in the configuration signal at a network node, the configuration signal processor associated with the network node: generating a reporting message containing the configuration data of its associated network node; and inserting each reporting message into the configuration signal; the configuration wavelength propagating the reporting messages in the configuration signal to the mapping processor; and upon receipt of one of the reporting messages in the configuration signal, the mapping means updating its network configuration data in accordance with the configuration data contained in the reporting message.
The invention may be summarized according to a eleventh broad aspect as a node for connection, in a WDM network which comprises a mapping processor, to a plurality of other nodes by wavelength division multiplexed (WDM) compatible optical fibre segments which carry a plurality of WDM compatible wavelengths capable of being modulated by signals and a configuration signal containing configuration data, comprising: a configuration signal processor for generating configuration data specific to its associated node and inserting the configuration data into the configuration signal, whereby the mapping processor may retrieve the configuration data from the configuration signal and determine the configuration of the node within the network.